1. Field of the Invention:
This invention pertains to the art of turbine airfoil vanes having a structure to promote their cooling.
2. Description of the Prior Art:
In the turbine art, it is well known that different stages of the stator vanes require different levels of cooling, with the vane structure with which this invention is concerned being of a character and in a stage calling for what those knowledgeable in the art would consider to be a low to moderate level of cooling. It is also known by those skilled in the art that with a given vane, the degree of cooling required at different locations on the vane may differ. Thus the leading edge region of the vane may have a relatively high heat load while downstream along the vane the heat load may be significantly lower.
It is the aim of the invention to provide a vane structure providing cooling techniques which allow a high degree of tailoring of the cooling design while also reasonably maximizing the thermal efficiency of the cooling system. It is to be understood that thermal efficiency is a term used to measure the coolant heat-up against the level of cooling achieved. In that sense, high thermal efficiencies imply relatively low quantities of cooling flow which leads to improved turbine performance. Thus, the structure of the invention is intended to provide cooling techniques which allow the maximum coolant heat-up to produce the maximum thermal efficiency.